The control system generally used on this type of wing comprises a rigid bar to each end of which is fixed a “rear line”, so-called for its remote end being connected to the wing behind its centre of pressure, and a single central line bifurcating into two lines called “front lines” for their remote ends being attached in front of the centre of pressure of the wing. The lower end of the central line is fixed to the user, as to a harness, and the bar slides along the single central line. Pivoting the bar to the left and right changes the direction of the wing, while extending and retracting the bar respectively decreases and increases the angle of attack of the wing relative to the wind, and thus regulates its power. A control system of this type is described, for instance, in FR2762583.
During use, for any given position of the bar along the central line it is desirable to be able to trim the wing, to provide for some variation of its angle of attack depending upon the wind conditions. This control system can be provided with means for adjusting the length of the central line to achieve this trim function. A trim adjustment strap arrangement may include fasteners and cooperating straps provided with two grips, such that pulling one grip shortens the central line from an initial length, and pulling the other grip releases the strap, allowing the central line to return to its initial length. The grips may be disposed on a mount that is fixed to the central line, such that they are positioned for ready access by the user.
However, fastening a grip mount to the centre line in a position which allows for ready trim adjustment can compromise the sliding movement of the bar along the centre line, as the bar abuts the mount. As a user could be towed into obstacles by wind gusts, the ability to quickly move the bar to a fully extended position is important as it allows a rapid reduction in power. In addition, in current designs the position of the grips can be pulled toward the user by adjustment of the trim and this can lead to tangling of the trim lines with other control lines. It will be understood therefore, that there is a need for a control system which addresses these requirements. The present invention proposes to address this need, or more generally, to provide an improved control system for a traction wing.